Hey guys,

I'm making an App that needs to be able to draw new graphics on top of the last set.

This is my current onDraw() method -

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protected void onDraw(Canvas canvas) {

    canvas.drawColor(Color.WHITE);

    //do some stuff here - this is all working ok

    canvas.drawLine(p1.x, p1.y, p2.x, p2.y, linePaint); 
}

Basically, I need to draw the new graphics as a layer on top of the last, so what I'm looking for is a way to carry the image of the last canvas to the current. There is a LOT of lines drawn every frame so simple drawing them all again isn't an option.

I have tried to figure it out myself using the canvas.setBitmap() method but it acts very funny.
This is what I put at the start of the onDraw() method, in my head it makes sense but it doesn't seem to do anything

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if(bitmap != null) {
        canvas.drawBitmap(bitmap, 0, 0, paint);
        canvas.setBitmap(bitmap);   
}

Any help is greatly appreciated

P.S if it's needed, the the class extends SurfaceView and implements SurfaceHolder.Callback

Is your 'bitmap' object a member variable that persists between onDraw calls?

Hi Marky, did you check the fingerpaint activity in apidemos?

Found the answer myself




This seems to work exactly as intended, it creates the effect of drawing on top of the old canvas continuously

Thanks for your help guys